Metathesis is one of a crucial reaction for the petrochemical industry, especially the cross-metathesis of ethene and butene which is an economical mean to produce highly demanded propene.
In a typical industrial metathesis process, the metathesis catalyst deactivates over time and hence requires periodically regeneration. Regeneration process generally involves treatment of the deactivated catalyst with an oxidizing gas at a high temperature to burn off poisonous substances and heavy deposits formed during the reaction. There is limited number of time that a catalyst should be subjected to such regeneration process because severe condition employed can alter some specific properties of the catalyst such as surface area and therefore reduce its efficiency.
It was found that during a reaction of ethene and butene to produce propene, 1,3-butadiene is formed as a byproduct. 1,3-butadiene, even at a low concentration in the system, induces coke formation on the catalyst surface which results in deactivation of the catalyst. To reduce such effect of 1,3-butadiene to the deactivation rate, the metathesis process can be carried out in the presence of hydrogen, as disclosed in patent publications number U.S. 20100145126 A1, U.S. 20130252804 A1, and U.S. 20100191030 A1. However, the presence of hydrogen would result in hydrogenation of propene product and therefore reduce propene product yield.